JP2024047987A - Method for producing useful components derived from lignin - Google Patents

Abstract

[Problem] To provide a method for efficiently producing an active ingredient from a raw material containing plant biomass containing lignin. [Solution] A method for producing a useful ingredient derived from lignin, comprising: (1) a solubilization step of treating a raw material containing plant biomass in a mixed solvent of water and an organic solvent selected from the group consisting of aliphatic alcohols, ketones, and cyclic ethers under the following conditions to obtain solubilized lignin; condition A: the concentration of the raw material charged to the solvent is 1% by mass or more and 20% by mass or less; condition B: the extraction temperature is 100°C or more and 350°C or less; condition C: the extraction time is 0.1 hours or more and 10 hours or less; (2) a first separation step of separating an organic phase containing the solubilized lignin; (3) a water-solubilization step of adding an aqueous solution of an alkali metal or alkaline earth metal hydroxide to the organic phase to water-solubilize the solubilized lignin; and (4) a second separation step of separating an aqueous phase containing the water-solubilized solubilized lignin. [Selected Figure] None

Description

The present invention relates to a method for producing useful components derived from lignin.

Lignin is one of the main components of plant cell walls and is a natural polymer whose constituent units are aromatic rings. Therefore, useful components such as phenols can be obtained by breaking down lignin into its constituent monomers. The obtained phenol derivatives can be used, for example, as monomer intermediates for highly functional aromatic polymers.

As one method for producing useful components derived from lignin, organosolv treatment using an organic solvent has been considered. For example, the present inventors have developed a two-phase organosolv treatment using a mixed solvent of water and an aliphatic alcohol such as 1-butanol (see, for example, Patent Document 1). In this method, the mixture is separated into an aqueous phase and an aliphatic alcohol phase at the treatment temperature, so that solubilized lignin (lignin decomposition product) can be selectively recovered in the aliphatic alcohol phase.

Patent No. 6344724

In Patent Document 1, the solubilized lignin dissolved in the aliphatic alcohol phase is recovered as a concentrate by removing the organic solvent under reduced pressure using an evaporator or the like (hereinafter, also referred to as the "concentration method"). As a result of further investigations by the present inventors, it was revealed that the monocyclic aromatic compounds in the solubilized lignin are also volatilized when the organic solvent is removed, and that further concentration causes the solubilized lignin to undergo aggregation and high molecular weight reactions, resulting in a decrease in the yield of useful components such as phenols derived from the lignin that are the target of reactions in subsequent processes.

The present invention aims to provide a method for efficiently producing active ingredients from raw materials containing plant biomass that contains lignin.

As a result of intensive research conducted by the present inventors in order to solve the above problems, the present inventions [1] to [3] below have been completed.
[1]
(1) a solubilization step of treating a raw material containing a plant biomass in a mixed solvent of water and an organic solvent selected from the group consisting of an aliphatic alcohol, a ketone, and a cyclic ether under the following conditions to obtain solubilized lignin;
Condition A: The concentration of the raw material in the solvent is 1% by mass or more and 20% by mass or less. Condition B: The extraction temperature is 100° C. or more and 350° C. or less. Condition C: The extraction time is 0.1 hours or more and 10 hours or less. (2) A first separation step of separating an organic phase containing solubilized lignin;
(3) a water-solubilizing step of adding an aqueous hydroxide solution of an alkali metal or alkaline earth metal to the organic phase to solubilize the solubilized lignin in water;
(4) a second separation step of separating an aqueous phase containing the solubilized lignin;
A method for producing a useful component derived from lignin, comprising:
[2]
The method according to [1], wherein the organic solvent is an aliphatic alcohol having 4 to 10 carbon atoms that undergoes two-phase separation from water at a temperature between 0° C. and 50° C.
[3]
(5) The production method according to [1] or [2], further comprising an oxidative decomposition step of oxidatively decomposing the solubilized lignin obtained in the second liquid separation step in the presence of a catalyst.

The present invention provides a method for efficiently producing active ingredients from raw materials containing plant biomass that contains lignin.

The following describes in detail the embodiments of the present invention. Note that the present invention is not limited to the following embodiments.

The method for producing a useful component derived from lignin according to the present embodiment includes the steps of:
(1) a solubilization step of treating a raw material containing a plant biomass in a mixed solvent of water and an organic solvent selected from the group consisting of an aliphatic alcohol, a ketone, and a cyclic ether under the following conditions to obtain solubilized lignin;
Condition A: The concentration of the raw material in the solvent is 1% by mass or more and 20% by mass or less. Condition B: The extraction temperature is 100° C. or more and 350° C. or less. Condition C: The extraction time is 0.1 hours or more and 10 hours or less. (2) A first separation step of separating an organic phase containing solubilized lignin;
(3) a water-solubilizing step of adding an aqueous hydroxide solution of an alkali metal or alkaline earth metal to the organic phase to solubilize the solubilized lignin in water;
(4) a second separation step of separating an aqueous phase containing the solubilized lignin;
Equipped with.
According to this production method, useful components derived from lignin can be produced efficiently.
Each step will be described in detail below.

<(1) Solubilization step>
Examples of plant biomass used as a raw material in the solubilization step of this embodiment include woody biomass and herbaceous biomass. Examples of woody biomass include cedar, cherry, eucalyptus, cypress, Japanese cypress, beech, and willow. Examples of herbaceous biomass include bamboo, palm trunks and empty bunches, palm fruit fibers and seeds, bagasse (residue after squeezing sugarcane juice), rice straw, wheat straw, corn residue (corn stover, corn cob, corn hull), jatropha seed coat and shell, switchgrass, erianthus, and residues generated during the extraction of vegetable oil from energy crops.

These plant biomasses are suitable because they usually contain about 15 to 40% by mass of lignin. The raw plant biomass may be pulverized. The raw plant biomass may be in any form, such as blocks, chips, or powder. The raw plant biomass may be pretreated to remove components other than lignin. For example, the plant biomass may be hydrothermally treated to remove hemicellulose contained in the raw material.

The solvent used in the solubilization step is a mixture of water and an organic solvent selected from the group consisting of aliphatic alcohols, ketones, and cyclic ethers.

As the aliphatic alcohol, for example, an aliphatic alcohol having 1 to 10 carbon atoms, preferably an aliphatic alcohol having 4 to 10 carbon atoms, more preferably an aliphatic alcohol having 4 to 6 carbon atoms can be used. Specific examples of the aliphatic alcohol include saturated straight-chain alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol; and saturated branched-chain alcohols such as isopropanol and isobutanol.

Specific examples of ketones include acetone, methyl ethyl ketone, and methyl butyl ketone. Specific examples of cyclic ethers include dioxane, tetrahydrofuran, and tetrahydropyran.

Among these organic solvents, aliphatic alcohols are preferred, with aliphatic alcohols with 1 to 10 carbon atoms being more preferred, and aliphatic alcohols with 4 to 10 carbon atoms that separate into two phases from water at temperatures between 0°C and 50°C being even more preferred. In particular, the use of aliphatic alcohols with 4 to 10 carbon atoms that separate into two phases from water is desirable because it allows the organic phase to be separated without any special operations in the first liquid separation step in the next step.

In an embodiment of the present invention, examples of water used as a solvent include tap water, industrial water, ion-exchanged water, and distilled water. The mixing ratio of water to organic solvent is preferably in the range of 0.5/1 to 45/1 in terms of molar ratio, water (mol)/organic solvent (mol), more preferably 0.7/1 to 30/1, even more preferably 0.9/1 to 20/1, and even more preferably 1.8/1 to 10/1.

In condition A, the concentration of the raw material in the solvent is 1% by mass or more and 20% by mass or less, preferably 2% by mass or more and 18% by mass or less, and more preferably 3% by mass or more and 15% by mass or less.

The reaction temperature in condition B is 100°C or higher and 350°C or lower, preferably 150°C or higher and 300°C or lower, and more preferably 170°C or higher and 270°C or lower.

The reaction time under condition C is from 0.1 to 10 hours, preferably from 0.2 to 8 hours, more preferably from 1 to 6 hours, and even more preferably from 1 to 3 hours.

In addition to the above conditions, the pressure of the reaction system in the solubilization step is preferably 0.5 MPa to 30 MPa. More preferable conditions are affected by the amount of water and alcohol and the temperature, so they should be set appropriately. The solubilization step can be carried out in air. It is preferable to carry out the solubilization step in an atmosphere with reduced oxygen by nitrogen purging in order to suppress polymerization due to oxidation reactions.

There are no particular limitations on the reaction method in the solubilization step. For example, a general batch reactor or semi-batch reactor can be used. It is also possible to apply a method in which a slurry consisting of the raw materials, water, and an organic solvent is reacted while being pushed out by a screw or pump. Furthermore, a stationary reaction is also possible.

<(2) First separation step>
In the first separation step, the organic phase containing the solubilized lignin obtained in the solubilization step is separated.

When a solvent that separates into two phases from water at temperatures between 0°C and 50°C is used as the organic solvent, the organic phase can be separated as is.

When a water-compatible solvent is used as the organic solvent, water and/or an organic solvent for extraction can be added until two phases are separated, and then the organic phase can be separated. Specific examples of organic solvents for extraction include diethyl ether, ethyl acetate, aliphatic alcohols having 4 to 10 carbon atoms (e.g., 1-butanol), toluene, and benzene.

After separation, extraction may be performed using an extraction solvent. If the amount of organic solvent in the separated organic phase is too large, the solvent may be evaporated using an evaporator or the like, but it is preferable to evaporate the solvent to a degree that does not cause the lignin to dry out in order to avoid evaporation of monocyclic aromatic compounds in the solubilized lignin.

The temperature of the organic phase during volatilization is preferably 30°C to 120°C, more preferably 40°C to 80°C, and even more preferably 40°C to 60°C, in order to reduce the time required for volatilization and the amount of the target substance volatilized.

The reduced pressure during volatilization is preferably 1 kPa to 20 kPa, more preferably 5 kPa to 15 kPa, in order to reduce the time required for volatilization and the amount of the target substance volatilized.

<(3) Water-solubilizing step>
In the water-solubilizing step, an aqueous solution of an alkali metal or alkaline earth metal hydroxide is added to the organic phase obtained in the first liquid-separation step to water-solubilize the solubilized lignin.

Examples of hydroxides of alkali metals include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of hydroxides of alkaline earth metals include magnesium hydroxide, calcium hydroxide, barium hydroxide, etc. Of these, sodium hydroxide and potassium hydroxide are preferably used.

The concentration of the aqueous alkali metal or alkaline earth metal hydroxide solution can be, for example, 0.5 to 5 mol/L.

<(4) Second liquid separation step>
In the second liquid-separation step, the aqueous phase containing the solubilized lignin obtained in the water-solubilizing step is separated. In the second liquid-separation step, an aqueous hydroxide solution of an alkali metal or alkaline earth metal is contacted with the organic phase multiple times to more reliably transfer the solubilized lignin to the aqueous phase. In addition, in order to remove an organic solvent such as an aliphatic alcohol contained in the aqueous phase, the above-mentioned extraction organic solvent may be contacted with the aqueous phase to perform further liquid separation.

<(5) Oxidative Decomposition Step>
The method for producing a useful component derived from lignin according to the present embodiment may further include an oxidative decomposition step in which the water-solubilized lignin obtained in the second liquid separation step is oxidatively decomposed in the presence of a catalyst and an oxidizing agent.

The solubilized lignin obtained after the second liquid separation step has already been decomposed to a certain degree, but in the oxidative decomposition step, it can be decomposed one more step in order to efficiently convert it into useful components with even lower molecular weights. Conventional lignin decomposition methods can be used as the oxidative decomposition method.

In this oxidative decomposition process, moderate decomposition is required; if the decomposition is too high, the decomposition of the desired useful components will proceed too far, resulting in a low yield. On the other hand, if the decomposition is too low, the reaction will not proceed, resulting in a low yield of useful components.

Catalysts that can be used in the oxidative decomposition process include basic catalysts, acidic catalysts, transition metal catalysts, lignin-decomposing enzymes, etc.

Examples of basic catalysts include metal hydroxides of alkali metals, alkaline earth metals, transition metals, etc., alkoxides of these metals, and nitrogen-containing organic base catalysts such as diazabicycloundecene (DBU) and diazabicyclononene (DBN).

Acid catalysts include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and organic acids such as toluenesulfonic acid and methanesulfonic acid.

Transition metal catalysts include salts of first transition metals such as manganese, chromium, iron, cobalt, and copper, second transition metals such as ruthenium, palladium, and rhodium, and third transition metals such as tungsten, osmium, iridium, and platinum, as well as their complexes, such as porphyrin complexes and salen complexes.

Examples of lignin-degrading enzymes include laccase, peroxidase, and oxidase.

Among these, first transition metals, metal salts, and metal complexes with appropriate decomposition properties are preferably used, and copper-based catalysts such as copper salts, copper complexes, and laccase are particularly preferred, with copper(II) hydroxide being particularly preferred from an industrial point of view.

Oxidizing agents include oxygen (air), hydrogen peroxide, ozone, hypochlorous acid, chloric acid, perchloric acid, nitric acid, chromates, dichromates, manganates, permanganates, etc.

These can be selected appropriately depending on the catalyst and reaction conditions, but oxygen and hydrogen peroxide are preferred due to their moderate oxidizing properties and ease of handling, with oxygen being particularly preferred.

The amount of catalyst in the oxidative decomposition process should be adjusted appropriately depending on the type of reaction, but when a metal, particularly a copper compound, is used, the weight percent concentration of the metal (copper) in the aqueous extract is 0.01 or more, more preferably 0.1 or more, even more preferably 0.2 or more, and 10 or less, more preferably 3 or less, even more preferably 1 or less.

The reaction temperature in the oxidative decomposition process can be appropriately adjusted depending on the type of reaction catalyst. When copper (II) hydroxide is used, the reaction temperature is 100°C or higher and 350°C or lower, preferably 150°C or higher and 300°C or lower, and more preferably 170°C or higher and 270°C or lower. In order to control the reaction, it is desirable to cool the reaction mixture immediately after heating it to the specified reaction temperature.

The oxidative decomposition process is preferably carried out in an atmosphere containing oxygen gas, but in consideration of reactivity and safety, an inert gas such as nitrogen gas may also be included to adjust the oxygen partial pressure.

There are no particular limitations on the reaction method used in the oxidative decomposition process. For example, a general batch reactor or semi-batch reactor can be used.

The method for producing useful components derived from lignin according to this embodiment suppresses the generation of coke, so the amount of coke adhering to the catalyst during the oxidative decomposition process can be reduced. It is widely known that the adhesion of coke is a major cause of reduced catalyst performance, and by applying the production method according to this embodiment, the functionality of the catalyst can be maintained for a long period of time.

The useful components derived from lignin obtained by the manufacturing method of this embodiment can be used as simple compounds such as vanillin and hydroxybenzoic acid, or can be chemically modified for use in applications with enhanced functionality. For example, they can be used as monomer intermediates for highly functional aromatic resin materials derived from renewable resources, not from petroleum or coal resources.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

Example 1 (Cedar, Hydrothermal Treatment, Organosolv Treatment (Water/BuOH), Liquid-Liquid Extraction Method)
<Lignin solubilization>
The raw material was cedar, which was crushed in a grinder and sieved to a powder of 300 μm or less. As a pretreatment, hydrothermal treatment was performed to remove hemicellulose contained in the raw material, and then lignin was solubilized by treatment with a water/1-butanol solvent (organosolv treatment).
The hydrothermal treatment was carried out using a SUS pressure batch reactor with an internal volume of 150 mL, with the raw material/solvent water ratio being 1/30 (weight ratio). After purging the reactor of the batch reactor with nitrogen, the temperature was raised to 165° C. and the reaction was carried out for 2 hours. The temperature inside the reactor was measured with a thermocouple, and the reaction time was the elapsed time after the temperature reached 165° C.
After the reaction, the product was separated into solid and liquid by filtration. The solid was washed with distilled water at room temperature for 15 minutes while stirring. This was repeated three times, and the solid was air-dried overnight and then vacuum-dried at 60°C for 3 hours, and then subjected to organosolv treatment.
The organosolv treatment was carried out using a 150 mL SUS pressure batch reactor with a solid content/solvent ratio of 1/30 (weight ratio) after hydrothermal treatment, and solvent: water/1-butanol ratio of 4/1 (molar ratio). After purging the reactor with nitrogen, the temperature was raised to 200°C and the reaction was carried out for 2 hours. The temperature inside the reactor was measured with a thermocouple, and the reaction time was the elapsed time after the temperature reached 200°C.
After the reaction was completed, the batch reaction vessel was immersed in ice water to cool, and after the temperature inside the vessel had dropped to about room temperature, the entire contents of the vessel were removed. The solid and liquid components were separated by filtration, and the filtrate was separated into liquid and liquid using a separatory funnel to obtain an aqueous phase and a 1-butanol phase (hereinafter referred to as "1-butanol solubles").

Liquid-liquid extraction
10 mL of the 1-butanol soluble matter was contacted with an equal amount of 2 mol/L aqueous sodium hydroxide solution to carry out liquid-liquid extraction at room temperature. This was repeated three times.
Next, in order to remove the 1-butanol dissolved in 30 mL of the sodium hydroxide extract, an equal amount of diethyl ether was contacted and liquid-liquid extraction was carried out at room temperature. This was repeated three times.

<Oxidative decomposition>
The oxidative decomposition reaction of the solubilized lignin extracted in the aqueous sodium hydroxide solution was carried out using a SUS pressure-resistant batch reactor equipped with a Teflon (registered trademark) inner cylindrical container.
30 mL of the raw material sodium hydroxide extract and 0.24 g of copper hydroxide (II) as a catalyst were introduced into the inner cylindrical container, the inside of the reactor was purged with nitrogen, and oxygen and nitrogen were introduced at 300 kPa each, and then the temperature was raised to 180 ° C. The temperature rise time was measured using a thermocouple of the reactor temperature and took about 1 hour. Immediately after reaching 180 ° C, the reaction was stopped by quenching the reactor. Then, the solid component and the liquid component were filtered and subjected to the following product analysis.

<Product Analysis>
(Solid Component)
The solid component was measured by measuring the adhering coke component using a thermogravimeter. After removing moisture by holding at 120°C for 120 minutes in a nitrogen atmosphere, the temperature was raised to 380°C at 15°C/min. The amount of coke was calculated from the weight (W _(T=120°C) ) when dried at 120°C and the weight loss (W _(T=380°C) -W _(T=120°C) ) when heated to 380°C using the following formula:

(Liquid components)
The collected liquid was diluted to 200 mL with distilled water, and an equal amount of tetrahydrofuran was added to increase the solubility of lignin and its decomposition products. The solution was acidified to about pH = 3 with a 30 wt % sulfuric acid solution to promote the release of the produced phenols.
The monocyclic phenols contained in the product solution after acidification were quantified by the internal standard method using a gas chromatograph equipped with a flame ionization detector (FID). At this time, products not containing aldehyde groups or carboxyl groups were quantified without derivatization treatment, and products containing aldehyde groups or carboxyl groups were quantified after derivatization treatment (silylation).
The derivatization treatment was carried out as follows. 1 mL of the product liquid after acidification was extracted three times with twice the amount of ethyl acetate to prepare an ethyl acetate soluble fraction. The solvent was removed from the ethyl acetate soluble fraction using an evaporator, and the fraction was then dissolved in pyridine. Thereafter, a silylating agent (N,O-bis(trimethylsilyl)trifluoroacetamide, BSTFA) was added, and the derivatization of the ethyl acetate soluble fraction was allowed to proceed at 60°C for 30 minutes.
The yield of phenols was calculated based on the carbon contained in the lignin in the raw material, and the lignin was quantified according to the conventional NREL method.

Comparative Example 1 (Cedar, Hydrothermal Treatment, Organosolv Treatment (Water/BuOH), Concentration Method)
<Lignin solubilization>
The same procedure as in Example 1 was followed.

<Concentration>
The solvent was removed from the 1-butanol soluble matter using an evaporator, and then vacuum drying was performed for 0.5 hours at 130° C. Then, in order to remove the remaining 1-butanol, an excess amount of acetone was added, and the solvent was removed again by vacuum drying at 130° C. for 0.5 hours to obtain a solubilized lignin concentrate.

<Oxidative decomposition>
As the raw material, 0.11 g of solubilized lignin concentrate obtained from the same amount of 1-butanol soluble matter (10 mL) as used in Example 1 was used, and added to 30 mL of 2 mol/L aqueous sodium hydroxide solution as a solvent.

<Product Analysis>
The same procedure as in Example 1 was followed.

Analysis results of liquid components in Example 1 and Comparative Example 1 The 1-butanol soluble fraction after the lignin solubilization step in Example 1, the liquid components in Example 1, and the liquid components in Comparative Example 1 were each analyzed, and the amounts of lignin-derived products detected (unit: C-mol%: lignin carbon basis) are shown in Table 1. As is clear from Table 1, a larger amount of useful components derived from lignin (phenols) was obtained in Example 1 compared to Comparative Example 1. Note that the 1-butanol soluble fraction contains other phenols (alkylphenols, alkylmethoxyphenols, and alkylcatechols), but these were not contained in the liquid components in Example 1 and Comparative Example 1, which were subjected to further treatment.

Example 2 (Cedar, organosolv treatment (water/EtOH), liquid-liquid extraction method)
<Lignin solubilization>
The raw material was cedar crushed with a grinder and sieved to obtain powder of 300 μm or less. The organosolv treatment was carried out using a SUS pressure batch reactor with an internal volume of 150 mL, with raw material/solvent = 1/30 (weight ratio) and solvent: water/ethanol = 1/1 (molar ratio). After purging the reactor of the batch reactor with nitrogen, the temperature was raised to 200 ° C and the reaction was carried out for 2 hours. The temperature inside the reactor was measured with a thermocouple, and the reaction time was the elapsed time after the temperature reached 200 ° C.
After the reaction was completed, the batch reaction vessel was immersed in ice water to cool it, and after the temperature inside the vessel had dropped to about room temperature, the entire contents of the vessel were removed. The solid matter and the liquid component were separated by filtration to obtain a water/ethanol soluble matter.

Liquid-liquid extraction
Six volumes (120 mL) of distilled water were added to 20 mL of the water/ethanol soluble matter, and liquid-liquid extraction was then carried out three times at room temperature using an equal volume (140 mL) of 1-butanol.
The solvent was removed from 420 mL of the 1-butanol phase using an evaporator, and the mixture was concentrated to a degree that did not cause the mixture to dry up. Then, 1-butanol was added to the mixture to make it 10 mL. An equal amount of 2 mol/L aqueous sodium hydroxide solution was contacted, and liquid-liquid extraction was performed at room temperature. This was repeated three times.
Next, in order to remove the 1-butanol dissolved in 30 mL of the sodium hydroxide extract, an equal amount of diethyl ether was contacted and liquid-liquid extraction was carried out at room temperature. This was repeated three times.

<Oxidative decomposition, product analysis>
The same procedure as in Example 1 was followed.

Comparative Example 2 (Cedar, Organosolv Treatment (Water/EtOH), Concentration Method)
<Lignin solubilization>
The same procedure as in Example 2 was followed.

<Concentration>
After the solvent was removed from the water/ethanol soluble fraction using an evaporator, the fraction was vacuum dried for 0.5 hours at 130° C. Then, in order to remove the remaining water and ethanol, an excess amount of acetone was added, and the fraction was vacuum dried again at 130° C. for 0.5 hours to remove the solvent, thereby obtaining a solubilized lignin concentrate.

<Oxidative decomposition>
As the raw material, 0.12 g of solubilized lignin concentrate obtained from the same amount of water/ethanol soluble matter (20 mL) as used in Example 2 was used, and added to 30 mL of 2 mol/L aqueous sodium hydroxide solution as a solvent. The rest was the same as in Example 1.

<Product Analysis>
The same procedure as in Example 1 was followed.

Analysis results of liquid components in Example 2 and Comparative Example 2 Analysis of the liquid components in Example 2 and Comparative Example 2 revealed that the amounts of vanillin were 3.2 C-mol% (lignin carbon basis) and 2.1 C-mol% (lignin carbon basis), respectively. As is clear from these results, compared to Comparative Example 2, a larger amount of vanillin was obtained in Example 2 as a useful component derived from lignin.

Analysis results of solid components in Examples 1 and 2 and Comparative Examples 1 and 2 The solid components in Examples 1 and 2 and the solid components in Comparative Examples 1 and 2 were analyzed, and the calculated coke amounts (unit: C-mol%) are shown in Table 2. As is clear from Table 2, the amount of coke deposition could be suppressed in the Examples.

Example 3 (Bagasse, Hydrothermal Treatment, Organosolv Treatment (Water/BuOH), Liquid-Liquid Extraction)
<Lignin solubilization>
Bagasse (residue after squeezing sugarcane juice) was used as the raw material, and the organosolv treatment conditions were solids after hydrothermal treatment/solvent = 1/10 (weight ratio), solvent: water/1-butanol = 8/1 (molar ratio).Otherwise, the same procedures as in Example 1 were carried out.

<Liquid-liquid extraction, oxidative decomposition, product analysis>
Regarding the product analysis, the analysis of the solid components was omitted. The rest of the analysis was carried out in the same manner as in Example 1.

Comparative Example 3 (Bagasse, Hydrothermal Treatment, Organosolv Treatment (Water/BuOH), Concentration Method)
<Lignin solubilization>
The same procedure as in Example 3 was followed.

<Concentration>
The same procedure as in Comparative Example 1 was carried out.

<Oxidative decomposition>
As the raw material, 0.62 g of solubilized lignin concentrate obtained from the same amount of 1-butanol soluble matter (10 mL) as used in Example 3 was used, and added to 30 mL of 2 mol/L aqueous sodium hydroxide solution as a solvent.

<Product Analysis>
The same procedure as in Example 3 was followed.

Analysis results of liquid components in Example 3 and Comparative Example 3 The 1-butanol soluble fraction after the lignin solubilization step in Example 3, the liquid components in Example 3, and the liquid components in Comparative Example 3 were each analyzed, and the amounts of lignin-derived products (unit: C-mol%: lignin carbon standard) detected are shown in Table 3. As is clear from Table 3, a larger amount of useful components derived from lignin (phenols) was obtained in Example 3 compared to Comparative Example 3. Note that the 1-butanol soluble fraction contains other phenols (alkylphenols, alkylmethoxyphenols, and alkylcatechols), but these were not contained in the liquid components in Example 3 and Comparative Example 3, which were subjected to further treatment.

Example 4 (willow, hydrothermal treatment, organosolv treatment (water/BuOH), liquid-liquid extraction method)
<Lignin solubilization>
Willow was used as the raw material. The rest of the experiment was carried out in the same manner as in Example 1.

<Liquid-liquid extraction, oxidative decomposition, product analysis>
Regarding the product analysis, the analysis of the solid components was omitted. The rest of the analysis was carried out in the same manner as in Example 1.

Comparative Example 4 (willow, hydrothermal treatment, organosolv treatment (water/BuOH), concentration method)
<Lignin solubilization>
The same procedure as in Example 4 was followed.

<Concentration>
The same procedure as in Comparative Example 1 was carried out.

<Oxidative decomposition>
As the raw material, 0.12 g of solubilized lignin concentrate obtained from the same amount of 1-butanol soluble matter (10 mL) as used in Example 4 was used, and added to 30 mL of 2 mol/L aqueous sodium hydroxide solution as a solvent. The rest was the same as in Example 4.

<Product Analysis>
The same procedure as in Example 4 was followed.

Analysis results of liquid components in Example 4 and Comparative Example 4 The 1-butanol soluble fraction after the lignin solubilization step in Example 4, the liquid components in Example 4, and the liquid components in Comparative Example 4 were each analyzed, and the amounts of lignin-derived products (unit: C-mol%: lignin carbon standard) detected are shown in Table 4. As is clear from Table 4, a larger amount of useful components derived from lignin (phenols) was obtained in Example 4 compared to Comparative Example 4. Note that the 1-butanol soluble fraction contains other phenols (alkylphenols, alkylmethoxyphenols, and alkylcatechols), but these were not contained in the liquid components in Example 4 and Comparative Example 4, which were subjected to further treatment.

Claims (3)

(1) a solubilization step of treating a raw material containing a plant biomass in a mixed solvent of water and an organic solvent selected from the group consisting of an aliphatic alcohol, a ketone, and a cyclic ether under the following conditions to obtain solubilized lignin;
Condition A: The concentration of the raw material in the solvent is 1% by mass or more and 20% by mass or less. Condition B: The extraction temperature is 100° C. or more and 350° C. or less. Condition C: The extraction time is 0.1 hours or more and 10 hours or less. (2) A first separation step of separating an organic phase containing solubilized lignin;
(3) a water-solubilizing step of adding an aqueous hydroxide solution of an alkali metal or alkaline earth metal to the organic phase to solubilize the solubilized lignin in water;
(4) a second separation step of separating an aqueous phase containing the solubilized lignin;
A method for producing a useful component derived from lignin, comprising: The method according to claim 1, wherein the organic solvent is an aliphatic alcohol having 4 to 10 carbon atoms that separates into two phases from water at temperatures between 0°C and 50°C. (5) The method according to claim 1 or 2, further comprising an oxidative decomposition step in which the water-soluble lignin obtained in the second liquid separation step is oxidatively decomposed in the presence of a catalyst.